The present invention relates to a glass, in particular a glass powder and a glass powder mixture, as well as their use to produce a glass ceramic, which may be used in particular as a resistor seal or ceramic solder in a spark plug.
German Published Patent Application No. 196 51 454 refers to a spark plug including an electrode connected across a terminal stud to an ignition line, with a resistor made of glass or a glass ceramic material having a high thermal stability being arranged between the electrode and the ignition line. A glass powder used as a starting material to produce the burn-off resistor may be metallized at the surface in a currentless operation.
The insulator base of a spark plug having a platinum center electrode develops temperatures of up to 950xc2x0 C. Because of these temperatures, options should be developed for contacting the center electrode, for producing a protruding burn-off resistor and for contacting the protruding burn-off resistor so that all these elements may tolerate an operating temperature of at least approximately 900xc2x0 C. for more than 2000 h. At the same time, the temperature of the spark plug during production should not exceed 950xc2x0 C. to prevent oxidation or deformation of the stud material.
In such spark plugs, the center electrode may be connected to the contact pin by diffusion welding. However, this may involve the problem of unwanted stresses and defects, since the coefficient of thermal expansion of the contact pin material may not be adequately adapted to the surrounding insulator.